AtkinsFact.org Makes "Unsupported" Arguments About Bone Risk
Atkins Ignores the Studies that Actually Measure Fracture Risk
Although some short-term studies reveal a net urinary calcium loss, long-term studies directly examining bone loss via DEXA scan (a superior indicator of bone health relative to urinary calcium) reveal no bone loss.
It is evident that you focus on indicators rather than endpoints. Your website, for example, discusses cardiac risk factors while failing to reference the one study that actually measured blood flow in the hearts of Atkins dieters--and showed a significant worsening of their heart disease. Although DEXA scans may be superior to urinary calcium measurements, arguably the best indicator would be assessing the risk of actually suffering a bone fracture. The Harvard Nurses' Health Study, which followed over 85,000 nurses for a dozen years, found that those eating just a serving of red meat a day had a significantly increased fracture risk.
While plant-based proteins did not show a deleterious effect, women in the Nurses' Study eating more animal protein had a significantly increased risk of forearm fracture. Another study following a thousand women linked meat consumption to hip fracture risk as well. "This suggests that an increase in vegetable protein intake" concluded the investigators, "and a decrease in animal protein intake may decrease bone loss and the risk of hip fracture." The only other study which looked at a large group of the general population over time found that those consuming as much meat and egg protein and as little calcium as do Atkins dieters doubled their risk of hip fracture.
You list 15 "selected" studies, though, that claim to show that the Atkins Diet doesn't adversely affect calcium and bone metabolism. Many of the conflicting results are based on what's called the "biphasic" effect of protein on bone health. Too much protein can increase fracture risk, but too little protein can as well, as protein makes up about 50% of bone tissue. So some studies involving elderly subjects who might be suffering from "protein undernutrition" have shown less bone loss or fracture risk with higher protein intakes, but low protein intake alone may be a marker of frailty or poor nutritional status in general. In fact studies show that protein malnutrition in the elderly may increase hip fracture rate just by increasing their propensity to fall.
Studies not restricted to the elderly, though, have more clearly found that those who eat the most animal protein may be putting their bones at risk.[962-964]